Device and method for instrument steralization

ABSTRACT

An electrolytic device and method for generating a sterilizing solution that utilizes hydrogen produced at the cathode as a further means to discharge biofilm material, microorganisms, and other organic material from the cathode surface. The device to be cleaned is typically electrically conductive and acts as a cathode, preferably by being in electrical contact with the cathode tray of the system. Aqueous Chlor-oxygen disinfectants produced within the device can be circulated through internal components of devices or instruments that may have internal passages. Gasses generated from the electrolysis operation, primarily hydrogen that is liberated at the cathode surface, are passively or forcibly vented from the system or are neutralized by a catalytic recombiner.

FIELD OF THE INVENTION

The present invention relates to an electrolytic method and apparatusfor sterilizing instruments or other objects.

BACKGROUND OF THE INVENTION

Note that the following discussion refers to a number of publicationsand references. Discussion of such publications herein is given for morecomplete background of the scientific principles and is not to beconstrued as an admission that such publications are prior art forpatentability determination purposes.

Electrolytic technology utilizing dimensionally stable anodes (DSA) hasbeen used for years for the production of chlorine and othermixed-oxidant solutions. Dimensionally stable anodes are described inU.S. Pat. No. 3,234,110 to Beer, entitled “Electrode and Method ofMaking Same,” whereby a noble metal coating is applied over a titaniumsubstrate.

An example of an electrolytic cell with membranes is described in U.S.Pat. RE 32,077 to deNora, et al., entitled “Electrode Cell with Membraneand Method for Making Same,” whereby a circular dimensionally stableanode is utilized with a membrane wrapped around the anode, and acathode concentrically located around the anode/membrane assembly.

An electrolytic cell with dimensionally stable anodes without membranesis described in U.S. Pat. No. 4,761,208 to Gram, et al., entitled“Electrolytic Method and Cell for Sterilizing Water.”

Various commercial electrolytic cells that have been used routinely foroxidant production may utilize a flow-through configuration that may ormay not be under pressure that is adequate to create flow through theelectrolytic device. Examples of cells of this configuration aredescribed in U.S. Pat. No. 6,309,523 to Prasnikar, et al., entitled“Electrode and Electrolytic Cell Containing Same,” and U.S. Pat. No.5,385,711 to Baker, et al., entitled “Electrolytic Cell for GeneratingSterilization Solutions Having Increased Ozone Content,” and many othermembrane-type cells.

In other configurations, the oxidant is produced in an open-type cell ordrawn into the cell with a syringe or pump-type device, such asdescribed in U.S. Pat. No. 6,524,475 to Herrington, et al., entitled“Portable Water Disinfection System.”

U.S. Pat. No. 6,736,966 to Herrington, et al., entitled “Portable WaterDisinfection System”, the specification and claims of which isincorporated herein by reference, describes disinfection devices thatutilize, in one instance, a cell chamber whereby hydrogen gas isgenerated during electrolysis of an electrolyte, and provides thedriving force to expel oxidant from the cell chamber through restrictivecheck valve type devices. In this configuration, unconverted electrolyteis also expelled from the body of the cell as hydrogen gas is generated.In an alternate configuration in the same application, hydrogen gaspressure is contained in a cell chamber during electrolysis, but thepressure within the cell chamber is limited by the action of a springloaded piston that continues to increase the volume of the cell chamberas gas volume increases. Ultimately, a valve mechanism opens, and thespring-loaded piston fills the complete volume of the cell chamberforcing the oxidant out of the cell chamber.

In the electrolytic cells utilizing titanium substrates with noble metalcoatings as the anode, the pH at the surface of the anode is typicallylow, on the order of approximately 3. With sufficiently high brineconcentration in the electrolyte, and sufficiently low voltage potentialat the anode surface, oxygen generated at the anode surface reacts toform hypochlorous acid and other chlor-oxygen compounds with no oxygengas liberated. Typical cathodes in these electrolytic cells may becomposed of titanium, noble metal coated titanium, catalyst coatedtitanium, nickel based allows such as Hastalloy, stainless steel, andother conductive materials impervious to high pH conditions. As thecathode, hydrogen is liberated at the cathode surface with a localizedhigh pH value at the cathode surface. During electrolysis, the metalcomprising the cathode is not oxidized or otherwise damaged duringelectrolysis despite the production of hydrogen at the cathode surface.Over time, titanium hydride can form at the surface of a bare titaniumcathode which may cause stress concentrations in the cathode surface. Topreclude this hydride formation, noble metal or catalyst coatings can beapplied to the cathode surface to prevent titanium hydride from formingon the cathode surface when the cathode substrate comprises titanium.

In a paper by Christine Rabinovitch, entitled “Electrochemical Controlof Staphylococcus epidermidis Biofilms”, published in the Proceedings ofthe Winter 2004 CBE Technical Advisory Conference, Feb. 5-6, 2004(Montana State University, Center for Biofilm Engineering), anelectrolytic method is described whereby a metallic coupon with abiofilm media grown on the surface of the metallic coupon is utilized asthe anode and/or cathode in an electrolytic reaction. When the metalliccoupon is utilized as the cathode, hydrogen liberated at the surface ofthe cathode forces partial or complete discharge and removal of thebiofilm from the metallic cathode surface. Sodium hydroxide with a highpH value that is produced at the cathode surface may also play a roledestruction of the biofilms. The author presents the limitations ofcorrosion and oxidation of the anode and/or cathode coupon during theelectrolytic process and questions the efficacy of chlorine speciesliberated at the anode surface as the source of destruction of biofilmat the anode.

An anti-biofouling system is described in U.S. Pat. No. 6,514,401 byChyou, et al whereby a graphite powder with binder is formed on anunderwater structure immersed in seawater. The conductive surface actsas an anode or cathode when electrical power is applied to form anelectrolytic surface whereby organisms are prohibited from forming onthe structure.

A medical instrument sterilizing system is described in U.S. Pat. No.6,056,866 by Maeda, et al whereby an electrolytic solution is generatedin an electrolytic cell, and a pumping device circulates thedisinfectant to a separate instrument tray where the instruments aresterilized.

SUMMARY OF THE INVENTION

The present invention is an instrument sterilization apparatuscomprising at least two electrodes wherein at least one electrodecomprises at least one cathode and at least one electrode comprises atleast one anode, the at least one cathode comprising a tray for holdingand providing electrical contact to an instrument and the at least oneanode comprising a tank; at least one insulator for separating the anodeand the cathode; and electrolyte disposed in the tank; wherein anelectrical potential between the anode and the cathode causes anelectrical charge to pass through the electrolyte, thereby generating atleast one oxidant in the electrolyte. The instrument preferably contactsthe tray, which is preferably porous.

The apparatus preferably further comprises an electrolyte storagecontainer which is preferably replaceable and which preferably furthercomprises a quick disconnect valve for allowing flow of the electrolyteto the tank only when the container is attached to the apparatus. Theapparatus preferably further comprises a microprocessor circuit thatidentifies the electrolyte storage container with the apparatus ormeasures a remaining volume of the electrolyte in the storage container.The apparatus optionally further comprises a brine generating device.The apparatus preferably further comprises an oxidant residual measuringdevice. The apparatus also preferably further comprises a vent orreactor for eliminating hydrogen gas generated during sterilization. Theapparatus preferably further comprises a tube for circulatingelectrolyte to the interior of an instrument.

The present invention is also a method for sterilizing and instrument,the method comprising the steps of disposing electrolyte in a tank;placing an instrument in a tray, the tray electrically insulated fromthe tank; providing an electrical potential between the tank and thetray so that the tank becomes an anode in an electrolytic reaction andthe tray becomes a cathode in the reaction; and generating at least oneoxidant in the electrolyte. The method preferably comprises placing theinstrument in electrical contact with the tray, in which case hydrogengas is preferably generated at the surface of the instrument.

The method preferably further comprises the step of measuring a value ofa characteristic of the electrolyte, and optionally adjusting theelectrical potential so that the value remains within a desired range.The method preferably further comprises the step of circulatingelectrolyte to an interior surface or interior component of theinstrument. The method preferably further comprises the step ofeliminating hydrogen gas generated during the reaction by venting orreacting the hydrogen gas. The method preferably further comprises thestep of rinsing the instrument with a sterile solution. The methodpreferably further comprises the step of drying the instrument withheated air.

An object of the present invention is to simplify sterilizingapparatuses by using sterilizing trays as the anode and cathode togetherin one unit.

A further object of the present invention is to utilize on or more ofhydrogen formation, chlorine or mixed oxidant formation, and sodiumhydroxide formation to sterilize instruments.

An advantage of the present invention is that the medical instruments orother devices requiring sterilization are preferably utilitzed as theanode and/or cathode in the electrolytic process, thus enhancing thesterilizing properties of the system.

Other objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate several embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating a preferred embodiment of the invention and are not to beconstrued as limiting the invention. In the drawings:

FIG. 1 is a system view of an embodiment of the present invention wherethe device to be sterilized is in electrical contact with a cathodetray.

FIG. 2 is a view of the quick disconnect electrolyte cartridge of thepresent invention.

FIG. 3 is a view of the present invention comprising optional heatersterile water rinse modules.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises an electrolytic device and method forgeneration of hydrogen gas at the cathode surface and oxidants producedat both the anode and cathode, which are utilized to expel contaminantssuch as biofilms and to disinfect surfaces, such as for sterilizinginstruments and other devices. The present invention preferably utilizesthe features of stable anodes and cathodes, formation of hydrogen formedat the cathode surface, formation of sodium hydroxide generated at thecathode surface, and formation of chlorine and mixed-oxidant speciesgenerated in a low pH environment at the anode surface as the basis forsterilizing instruments or objects. As used throughout the specificationand claims, to “sterilize” means to sterilize, disinfect, or otherwiseclean. As used throughout the specification and claims, “instrument”means any object or device to be sterilized, including but not limitedto surgical instruments, endoscopes, utensils, and the like.

In the present invention the instrument to be sterilized is preferablyused as the cathode in an electrolytic process. Hydrogen liberated atthe cathode (instrument) surface discharges all materials, including butnot limited to biofilms, from the instrument surface. Sodium hydroxideat high pH acts as a caustic substance to disinfect the device. Chlorineliberated at the anode surface at low pH (acidic) disinfectsmicroorganisms on the device surface, or creates a disinfectant in thesolution to kill microorganisms on the device surface and microorganismsor organic material in the electrolyte fluid. The instrument ispreferably at least partially electrically conductive, and morepreferably at least partially metallic. Instruments preferably comprisetitanium, Hastalloy, stainless steel, conductive plastic, or othercaustic (high pH) resisting materials. Plastic components of theinstruments are optionally impregnated with titanium, hastalloy,stainless, carbon, or other conductive filings that then make theplastic electrically conductive to facilitate hydrogen formation at thesurface of the plastic. An oxidant solution pump is preferably utilizedto pump oxidant to the internal components and surfaces of instrumentssuch as endoscopes. A hydrogen vent and recombiner device preferablyconverts hydrogen liberated in the electrolysis process, and oxygen fromthe atmosphere, to water vapor to mitigate the dangers associated withhydrogen gas.

Referring to FIG. 1, tank 12 preferably acts as the anode and preferablycomprises a catalytic coating on its interior surface, which containselectrolyte 62. Inner tray 14 preferably comprises the primary cathode.Inner tray 14 preferably comprises a suitable cathode material,preferably titanium, and further preferably comprises perforations 50that allow electrolyte 62 to freely flow around both the outside and theinside of inner tray 14. Inner tray 14 is optionally removeable. Byapplication of the appropriate positive (preferably direct current)voltage and current density to tank 12 and negative (preferably directcurrent) voltage and current density to inner tray 14, the electrolyteis preferably converted to chlorine-based mixed-oxidant species withinelectrolysis space 26.

When instrument 38 is placed within inner tray 14, instrument 38preferably comes into electrical contact with inner tray 14 and therebyalso acts as a cathode in the electrolysis process. Alternatively, innertray 14 is not used, and negative DC electrical power is directlyapplied to instrument 38 via cathode electrical conductor 18; in thiscase, instrument 38 preferably rests in a perforated plastic mesh,perforated Teflon liner, or the like, or rests on insulating supports,within tank 12 so there is no electrical contact between tank 12 (theanode) and instrument 38 (the cathode).

Instrument 38 is preferably constructed of a conducting material, or canbe produced from a plastic material with additives to make the plasticcomponents electrically conductive. In the electrolysis process of thepresent invention, hydrogen is liberated at the surface of the cathode.Hydrogen bubbles preferably act as a physical scrubbing agent to removematerial from the surface of instrument 38. Such material includes butis not limited to organic materials, biological materials, biofilms, orother organic matter. The organic contaminants are then transferred tobulk electrolyte 62, which is preferably concurrently converted to achlorine-based mixed oxidant solution. The mixed-oxidant solution thenacts as a disinfecting solution to destroy the organic contaminantswithin bulk electrolyte 62.

Tank 12, which preferably serves as the anode in the system, preferablymechanically supports and is electrically insulated from inner tray 14,which preferably serves as the cathode, by a plurality of insulators 20,22. Alternatively one insulator may be disposed on the inside of tank12, for example in a ring shape, for supporting inner tray 14. Althoughinner tray 14 is preferably attached to insulators 20, 22, it mayoptionally removeably rest on insulators 20, 22, optionally via a lip onthe tray or by some other means. Positive DC electrical power ispreferably applied to tank 12 via anode electrical conductor 16.Negative DC electrical power is preferably applied to inner tray 14 viacathode electrical conductor 18. Power to tank 12 and inner tray 14 ispreferably regulated and controlled by controller 56, which alsopreferably controls the system.

The present system and method preferably comprise a batch process thatmaintains a desired residual oxidant value, preferably a residualchlorine value, within electrolyte 62. The sterilizing device of thepresent invention preferably comprises an oxidant residual monitoringdevice 70, which preferably comprises an oxidation reduction potential(ORP) sensor or a chlorine sensor, preferably mounted on an integratedcircuit device (for example, a chlorine sensor-on-a-chip). The ORP valuemay optionally be adjusted for variations in temperature and pH ofelectrolyte 62.

Monitoring device 70 may be then used in a feedback system forcontrolling the electrolytic operation of the system. Oxidant residualmonitoring device 70 monitors the chlorine residual value, preferablyvia controller 56. If the chlorine residual value is below the desiredvalue, controller 56 provides additional power to tank 12 and inner tray14 thereby producing additional oxidant in electrolyte 62. In this modeof operation, neither the oxidant demand nor the volume or fluid levelof electrolyte 62 are important to maintaining the desired chlorine orother oxidant residual value. If the chlorine residual value is notsufficient, controller 56 continues making oxidant until the desiredchlorine residual is maintained.

Circulation of electrolyte 62 in the device may be desirable. Forexample, internal components of endoscope 100 used for some medicalprocedures may become contaminated. By circulating electrolyte 62 to theinternal surface of endoscope 100, the internal components of endoscope100 are cleaned in the same manner as the exterior surface of endoscope100. To facilitate circulation of electrolyte 62, pump 42 preferablytransfers electrolyte 62 through passage 40 from tank 12 and through3-way valve 52 and passage 44 into tube 46 and out of tube end 48. Tubeend 48 is preferably connected to a hollow passage of a medicalinstrument, such as endoscope 100, so that sterilizing fluid can beflushed through the internal components of the medical instruments. Whenthe flushing cycle is complete, electrolyte 62 may optionally bediscarded from the sterilizing tray by switching the valve position of3-way valve 52 and thereby discharging electrolyte through outlet 54.Pump 42 and 3-way valve 52 are preferably controlled by controller 56.

Electrolysis typically generates hydrogen gas at the cathode electrode.Hydrogen gas is explosive at a wide range of pressures. Only below aconcentration of approximately 4.1% hydrogen in the atmosphere, or abovea concentration of about 74.2% hydrogen in the atmosphere, is the gasmixture not combustible. Thus, for proper safety, hydrogen containmentor elimination is desirable. In the present invention, hydrogen gasaccumulates in the upper space 64 of the sterilizing unit and iscontained there by device cover 24. The hydrogen gas is preferablytransferred from upper space 64 via passage 28 to catalytic recombiner34, which is preferably utilized to burn hydrogen with oxygen to producewater vapor, which is preferably discharged out of port 36. Normalatmospheric air is preferably drawn into blower 32 and transferredthrough passage 30 to provide the oxygen source for reacting withhydrogen within catalytic combiner 34. In this manner, hydrogen isdestroyed and is no longer available as a fuel source for an explosiveevent. Alternatively, a vent pipe transfers hydrogen from upper space 64to a ventilation duct and discharges it outside of the room or facilitythat houses the sterilizing device.

Electrolyte 62 preferably comprises a sodium chloride brine solution.Other halide salts may alternatively be utilized to produce electrolyte62. For medical applications, a preferred source of brine solution is0.9% saline Ringers solution. Pre-made electrolyte solution 60 ispreferably stored within electrolyte storage container 58 for use withthe present invention. Referring to FIG. 2, electrolyte storagecontainer 58 is optionally attached to the sterilizing tray via support74 and is preferably quickly removable from the system by means of quickdisconnect self-sealing valve 68 for subsequent replacement by a newelectrolyte storage container. Alternatively, electrolyte storagecontainer 58 may be refillable. Electrolyte storage container 58preferably comprises vent valve 66 that allows the introduction of airinto electrolyte storage container 58 as pre-made electrolyte solution60 is drawn out of container 58 thereby avoiding negative pressure incontainer 58.

Container 58 optionally comprises microchip device 72 that identifiescontainer 58 with the total system, and preferably provides forelectronic monitoring of the volume of the contents of container 58based on the number of cycles of the system or another property.Electrolyte storage container 58 is optionally replaced with a brinegenerating device. Such brine generating device is preferably filledwith salt, preferably a halogen salt, and mixes water with the halogensalt to produce a liquid brine solution. The liquid brine solutionperforms as electrolyte 62.

As shown in FIG. 3, the sterilizing system optionally comprisesheater/dryer module 80 and sterile water purge module 82. In thisembodiment, the initial sterilizing cycle is preferably followed bydraining of electrolyte via 3-way valve 52 through outlet 54 andsubsequent closure of 3-way valve 52. In the second step, 3-way purgevalve 86 is opened to allow transfer of sterile water, or anothersterile solution, from sterile water purge module 82 for rinsing tank12; 3-way purge valve 86 preferably prevents the sterile water fromexiting via outlet 54. After purging, 3-way purge valve 86 is preferablyopened to drain sterile water via outlet 54. In the final step, 3-wayvalve 84 is preferably opened to allow heated dry air from heater/dryermodule 80 to dry the instruments within tank 12.

The present invention optionally comprises one or more oxidant storagecontainers and at least one port for injecting one or more oxidants intoan instrument, including but not limited to a closed fluid body, an openfluid body, a pipe with fluid flowing therein, a sump, a basin, atrough, or a plenum.

The present invention is particularly applicable to medical instrumentsterilization. However, it will be obvious to those versed in the artthat this invention can be utilized in a variety of applications whereother objects or devices need to be sterilized or otherwise cleaned,including but not limited to dishwashing machines, cabinets, or otherconfigurations.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverin the appended claims all such modifications and equivalents. Theentire disclosures of all references, applications, patents, andpublications cited above are hereby incorporated by reference.

1. An instrument sterilization apparatus comprising: at least twoelectrodes wherein at least one electrode comprises at least one cathodeand at least one electrode comprises at least one anode, said at leastone cathode comprising a tray for holding and providing electricalcontact to an instrument and said at least one anode comprising a tank;at least one insulator for separating said anode and said cathode; andelectrolyte disposed in said tank; wherein an electrical potentialbetween said anode and said cathode causes an electrical charge to passthrough said electrolyte, thereby generating at least one oxidant in theelectrolyte.
 2. The apparatus of claim 1 further comprising anelectrolyte storage container.
 3. The apparatus of claim 2 wherein saidelectrolyte storage container is replaceable.
 4. The apparatus of claim3 wherein said electrolyte storage container further comprises a quickdisconnect valve for allowing flow of said electrolyte to said tank onlywhen said container is attached to said apparatus.
 5. The apparatus ofclaim 2 further comprising a microprocessor circuit that identifies saidelectrolyte storage container with said apparatus or measures aremaining volume of said electrolyte in said storage container.
 6. Theapparatus of claim 1 further comprising a brine generating device. 7.The apparatus of claim 1 wherein the instrument contacts said tray. 8.The apparatus of claim 1 further comprising an oxidant residualmeasuring device.
 9. The apparatus of claim 1 further comprises a ventor reactor for eliminating hydrogen gas generated during sterilization.10. The apparatus of claim 1 wherein said tray is porous.
 11. Theapparatus of claim 1 further comprising a tube for circulatingelectrolyte to the interior of an instrument.
 12. A method forsterilizing and instrument, the method comprising the steps of:disposing electrolyte in a tank; placing an instrument in a tray, thetray electrically insulated from the tank; providing an electricalpotential between the tank and the tray so that the tank becomes ananode in an electrolytic reaction and the tray becomes a cathode in thereaction; and generating at least one oxidant in the electrolyte. 13.The method of claim 12 wherein the placing step comprises placing theinstrument in electrical contact with the tray.
 14. The method of claim13 further comprising the step of generating hydrogen gas at the surfaceof the instrument.
 15. The method of claim 12 further comprising thestep of measuring a value of a characteristic of the electrolyte. 16.The method of claim 15 further comprising the step of adjusting theelectrical potential so that the value remains within a desired range.17. The method of claim 12 further comprising the step of circulatingelectrolyte to an interior surface or interior component of theinstrument.
 19. The method of claim 12 further comprising the step ofeliminating hydrogen gas generated during the reaction by venting orreacting the hydrogen gas.
 20. The method of claim 12 further comprisingthe step of rinsing the instrument with a sterile solution.
 21. Themethod of claim 12 further comprising the step of drying the instrumentwith heated air.